A recent publication from Bill Kaiser’s and Ed Mocarski’s labs in Cell Host & Microbe touches on a concept that needs explaining: oncolytic viruses.
Viruses have been subverting the machinery of healthy cells for millions of years, and many viruses tend to infect particular tissues or cell types. So they are a natural starting point for researchers to engineer oncolytic viruses, which preferentially infect and kill cancer cells.
Several oncolytic viruses have progressed to advanced clinical trials. Amgen’s “T-Vec”, a modified herpes simplex virus, could be the first to be approved by the FDA this year based on its efficacy against metastatic melanoma. Read more
Emory dermatologist Jack Arbiser has been investigating (and recently patented) inhibitors of the enzyme Nox4 as potential anti-cancer drugs.
Nox4 has emerged as a potential therapeutic target in ataxia-telangiectasia, a rare multifaceted genetic disorder that leads to neurological problems, a weakened immune system and an increased risk of cancer. Ataxia-telangiectasia (or A-T) is caused by a defect in ATM, a sensor responsible for managing cells’ responses to DNA damage and other kinds of stress.
In a February PNAS paper, researchers at the National Cancer Institute led by William Bonner report that a Nox4 inhibitor can dial back oxidative stress and DNA damage in ataxia-telangiectasia cells, and can reduce cancer rates in a mouse model of the disease. Nox4 was activated in cells and tissue samples obtained from A-T patients.
The Nox4 inhibitor the NCI team used, fulvene-5, was originally identified by Arbiser in a 2009 Journal of Clinical Investigation paper as a possible treatment for hemangiomas, a common tumor in infants that emerges from blood vessels.
David Lambeth, an expert on the NADPH oxidase family of enzymes, and his team recently described Nox4 as an “hydrogen peroxide-generating oxygen sensor.”
It arises from what scientists previously described as “junk DNA” or “the dark matter of the genome,” but this gene is definitely not junk. The gene Gas5 acts as a brake on steroid hormone receptors, making it a key player in diseases such as hormone-sensitive prostate and breast cancer.
Unlike many genes scientists are familiar with, Gas5 does not encode a protein. It gets transcribed into RNA, like many other genes, but with Gas5 the RNA is what’s important, not the protein. The RNA accumulates in cells subjected to stress and soaks up steroid hormone receptors, preventing them from binding DNA and turning genes on and off.
Emory researchers have obtained a detailed picture of how the Gas5 RNA interacts with steroid hormone receptors. Their findings show how the Gas5 RNA takes the place of DNA, and give hints as to how it evolved.
The results were published Friday in Nature Communications.
Scientists used to think that much of the genome was “fly-over country”: not encoding any protein and not even accessed much by the cell’s gene-reading machinery. Recent studies have revealed that a large part of the genome is copied into lincRNAs (long intergenic noncoding RNAs), of which Gas5 is an example. Read more
People interested in drug discovery may have heard of “Lipinski’s rule of five,” a rough-and-ready set of rules for determining whether a chemical structure is going to be viable as a orally administered drug or not. They basically say that if a compound is too big, too greasy or too complicated, it’s not going to get into the body and make it to the cells you want to affect. These guidelines have been the topic of much debate among medicinal chemists and pharmacologists.
The namesake for this set of rules, Chris Lipinski, will be speaking at Winship Cancer Institute Wednesday afternoon (4:30 pm, Nov 5, C5012) on “The Rule of 5, Public Chemistry-Biology Databases and Their Impact on Chemical Biology and Drug Discovery.” Lipinski spent most of his career at Pfizer (while there, he published the “rule of 5 paper“) and now is a consultant at Melior Discovery.
Doctors are using a “divide and conquer” strategy against lung cancer, and in some corners of the battlefield, it’s working. A few mutations – genetic alterations in the tumor that don’t come from the patient’s normal cells — have been found for which drugs are effective in pushing back against the cancer.
However, most lung tumors do not have one of these mutations, and response rates to conventional chemotherapy in patients with advanced lung cancer are poor. Generally, only around 20 percent of patients show a clinical response, in that the cancer retreats noticeably for some time.
Johann Brandes and colleagues at Winship Cancer Institute have been looking for biomarkers that can predict whether an advanced lung tumor is going to respond to one of the most common chemotherapy drug combinations, carboplatin and taxol.
“The availability of a predictive test is desirable since it would allow patients who are unlikely to benefit from this treatment combination to be spared from side effects and to be selected for other, possibly more effective treatments,” Brandes says.
Brandes’ team’s data comes from looking at patients with advanced lung cancer at the Atlanta VAMC from 1999 to 2010. In a 2013 paper in Clinical Cancer Research, the team looked at a protein called CHFR. It controls whether cells can reign in their cycles of cell division while being bombarded with chemotherapy.
In this group being treated with carboplatin and taxol, patients who had tumors that measured low in this protein lived almost four months longer, on average, than those who had tumors that were high (9.9 vs 6.2 months).
His team takes a similar approach in a new paper published in PLOS One. Postdoc Seth Brodie is the first author of the PLOS One paper; he is also co-first author of the CHFR paper along with Rathi Pillai. Read more
The Spectropen, a hand-held device developed by Emory and Georgia Tech scientists, was designed to help surgeons see the margins of tumors during surgery.
Some of the first results from procedures undertaken with the aid of the Spectropen in human cancer patients were recently published by the journal PLOS One. A related paper discussing image-guided removal of pulmonary nodules was just published in Annals of Thoracic Surgery.
To test the Spectropen, biomedical engineer Shuming Nie and his colleagues have been collaborating with thoracic surgeon Sunil Singhal at the University of Pennsylvania.
As described in the PLOS One paper, five patients with cancer in their lungs or chest participated in a pilot study at Penn. They received an injection of the fluorescent dye indocyanine green (ICG) before surgery.
ICG is already FDA-approved for in vivo diagnostics and now used to assess cardiac and liver function. ICG accumulates in tumors more than normal tissue because tumors have leaky blood vessels and membranes. The Spectropen shines light close to the infrared range on the tumor, causing it to glow because of the fluorescent dye.
[This technique resembles the 5-aminolevulinic acid imaging technique for brain tumor surgery being tested by Costas Hadjipanayis, described in Emory Medicine.]
In one case from the PLOS One article, the imaging procedure had some tangible benefits, allowing the surgeons to detect the spread of cancerous cells when other modes of imaging did not. Read more
In Greek mythology, the chimera was a monstrous fire-breathing creature composed of the parts of three animals: a lion, a snake and a goat.
Adoptive cell transfer is advancing as a cancer immunotherapy technique. It involves removing some of a patient’s immune cells, culturing them in the laboratory, and then infusing the cells back into the patient. The idea is to enhance the ability of the immune cells to attack the tumors far beyond what the immune system was able of doing on its own.
Two promising examples are the National Cancer Institute’s approach of treating advanced melanoma with IL-2-stimulated immune cells, and several investigators’ approach of genetically engineering T cells to attack leukemias or lymphomas.
Jacques Galipeau and colleagues at Winship Cancer Institute have developed a chimeric molecule for stimulating immune cells, which appears to have unique powers beyond simply the sum of its two parts. The molecule is called GIFT4, a fusion of the immune signaling molecules GM-CSF (often used in cancer treatment) and IL-4.
In honor of Fathers’ Day, we are examining a connection between two older-male-centric topics: statins and prostate cancer.
Statins are a very widely prescribed class of drugs used to lower cholesterol levels, for the purpose of preventing cardiovascular disease. In cell culture, they appear to kill prostate cancer cells, but the epidemiological evidence is murkier. Statin effects on prostate cancer incidence have been up in the air, but recent reports point to the possibility that starting statins may slow progression, after a man has been diagnosed with prostate cancer.
Winship Cancer Institute researchers have some new results that shed some light on this effect. John Petros, Rebecca Arnold and Qian Sun have found that mutations in mitochondrial DNA make prostate cancer cells resistant to cell death induced by simvastatin [Zocor, the most potent generic statin]. Sun recently presented the results at the American Urological Association meeting in Orlando.
In other forms of cancer such as breast and lung cancer, genomic profiling can determine what DNA mutations are driving cancer growth and what drugs are likely to be effective in fighting the cancer. The prostate cancer field has not reached the same point, partly because prostate cancers are not generally treated with chemotherapy until late in the game, Petros says. But potentially, information on mitochondrial mutations could guide decisions on whether to initiate statin (or another) therapy.
“This is part of our soapbox,” he says. “When we are looking at mutational effects on prostate cancer, let’s be sure to include the mitochondrial genome.”
Winship’s Carlos Moreno and his colleagues are working on the related question of biomarkers that predict prostate cancer progression, after prostatectomy surgery and potentially after just a biopsy.
The hormone progesterone could become part of therapy against the most aggressive form of brain cancer. High concentrations of progesterone kill glioblastoma cells and inhibit tumor growth when the tumors are implanted in mice, researchers have found.
The results were recently published in the Journal of Steroid Biochemistry and Molecular Biology.
Glioblastoma is the most common and the most aggressive form of brain cancer in adults, with average survival after diagnosis of around 15 months. Surgery, radiation and chemotherapy do prolong survival by several months, but targeted therapies, which have been effective with other forms of cancer, have not lengthened survival in patients fighting glioblastoma.
The lead author of the current paper is assistant professor of emergency medicine Fahim Atif, PhD. The findings with glioblastoma came out of Emory researchers’ work on progesterone as therapy for traumatic brain injury and more recently, stroke. Atif, Donald Stein and their colleagues have been studying progesterone for the treatment of traumatic brain injury for more than two decades, prompted by Stein’s initial observation that females recover from brain injury more readily than males. There is a similar tilt in glioblastoma as well: primary glioblastoma develops three times more frequently in males compared to females.
These results could pave the way for the use of progesterone against glioblastoma in a human clinical trial, perhaps in combination with standard-of-care therapeutic agents such as temozolomide. However, Stein says that more experiments are necessary with grafts of human tumor cells into animal brains first. His team identified a factor that may be important for clinical trial design: progesterone was not toxic to all glioblastoma cell lines, and its toxicity may depend on whether the tumor suppressor gene p53 is mutated.
Atif, Stein, and colleague Seema Yousuf found that low, physiological doses of progesterone stimulate the growth of glioblastoma tumor cells, but higher doses kill the tumor cells while remaining nontoxic for healthy cells. Similar effects have been seen with the progesterone antagonist RU486, but the authors cite evidence that progesterone is less toxic to healthy cells. Progesterone has also been found to inhibit growth of neuroblastoma cells (neuroblastoma is the most common cancer in infants), as well as breast, ovarian and colon cancers in cell culture and animal models.